Permissive automatic train-control system



T 1929- c. s. BUSHNELL PERMISSIVE AUTOMATIC TRAIN CONTROL SYSTEM Filed Nov. 27, 1925 Patented Oct. l, i929 man:

WAY SIGNAL ooMrANY, or ,nocrrns'rnmnnw your PERMISSIVE AUTOMATIC 'r AIn-ooivraor. sysrn u Application filed November, 27, 1925; Serial n '."*Z/,1 ,75,1. j

This invention relates to automatic train control and more particularly concerns an automatic train control system of the well known continuous inductive type.

Modern systems of automatic train control have in general been designed to safeguard and facilitate train operation and to provide an additional safety control over that afforded by the engineer in-his observance of the wayside signals and his control of the train in accordance with the indications thereof. It is therefore thought advisable to arrange the automatic train con-' trol system in such a manner thatthe proper observance of wayslde signals by the engiuser is encouraged, and the has been accomplished in many systems by providing a. systom which incorporates the feature of acl cnowledgement; that is, a system in which the engineer may, by the performance of some suitable acknowledging act when a signal presenting an unfavorable aspect is encountered, avoid an automatic brake applica? tion, a restrictive speed limit-or other penalty or annoyance.

In many of the systems incorporating the acknowledging feature described above, it has been found that although the engineer is required to acknowledge the first unfavorable signal which he encounters, the acknowledged condition of the apparatus, persists, and if successive unfavorable signals are encountered, no further acknowledgment is -r'equircd. In other Words, in these systems, the engineer not encouraged or required to remain alert and vigilant in his observation of successive danger or caution signals provided he has properly acknowledged the first of these unfavorable signals.

With the above and other considerations in mind, it is proposed in accordance with the present invention. to provide an autoinatictrain control system of the continuous inductive type in which the engineer may avoid an automatic brake application by properly acknowledging each unfavorable signal indication, and in which the acknowledgment of successive unfavorable signal indications is required to continue the avoidance of an automatic brake application.

More specifically it is proposed to provide a system in which a stick re'layis energized if an unfavorable signal is properly-acknowledged and in which'thisstick relay is maintained energized at successiveunfavorable signals only if the acknowledging act is repeated at such unfavorable signals.

Other specific objects, advantages and characteristic features of the inventionv will i become apparent as the description thereof progresses. i a v a In describing the invention'in detail, reference will be madeto the accompanying drawing inwhjich asingle figure representing the cancarried and trackway apparatus of a systern of train control embodying the present invention in a diagrammatic and conven tional manner has beenlsho wn.

Referring, now more particularly to the trackway apparatus shown in the drawings, thetrack rails 1 havebeen show-n divided into the usual blocks ,by the insulating joints 2, the-block Ian d the ends of the two adjacentblocks H and J having been shown. As e dev c an pparat used in c n tion with the successive blocks are identical,

like reference characters having distinctive exponents are used to designate the corresponding elements in the successive blocks.

The usual track relays3fhave been shown connected across theftrack rails at the entrance ends of the blocksflf, The track circuit current for operating these-relays is supplied by the batteries, 4: connected across the track rails ,atlthe exit ends-of the blocks inseries with. the secondary winding of the trans former v5. T;he ,usual track phase train control current isfsuppli'ed-to'thetwo track rails ofeach ,block in series through ,the trans-' former 5, thecontact glingers6 and 7 and front contacts of the track relay 3 and the. transformer 8 connected to the transmission line 9, this circuit. being obvious from the drawings. Itis obvious, that if atrai'n is located in a given block,-tl 1e-track circuit current is shunted from the track rails by thewheels and axles of such train and the track relay 3 at the entrance .end of this block is de energized. The de-energization ofjthe trackjr-e lay at the entrancelend of agiyen'block causes the track phase train control current to be cut off from the track rails at the track relay contact fingers 6 and v7, so that with a train located in a given bloc-k no train control current flows in the track rails of that portion of the given block in the rear of the train or in the track rails of the first block in the rear.

Wayside signals of some suitable type are preferably employed in connection with the train control system of the present invention, and for the purpose of illustration, semaphore wayside signals of the well known type have been illustrated at Z. Since the controlling and operating devices and circuits for these wayside signals are well known to those skilled in the art and form no part of the present invention, a showing of these devices and circuits has been omitted, it being understood that a signal at the entrance end of an occupied block or at the entrance end of the first block to the rear of an occupied block is automatically moved to a position to give a'suitable, unfavorable indication.

Acknowledging loops 10 are provided near the exit end of each block. These acknowledging loops may take any suitable form, and as illustrated, comprise wires which are located in close proximity to the track rails and which extend for a suitable distance, preferably 200 feet or more, from the exit end of the block. These acknowledging loops are continuously supplied with alternating current of train control frequency through the transformers 11, connected to the transmis- .1 sion line 9, and thus present a permanent mag netic field in close proximity to the track rails near the exit end of each block. It should be understood that the track rails themselves might be provided with insulated sections near the exit end of each block, and thatthese sections might heperma'nently energized to form acknowledging loops. The function and operation of the acknowledging loops will be explained in connection with the operation of the system as a whole. e

Referring now to the car-carried apparatus of the present invention, a railway vehicle has been conveniently represented bythe wheelsand axles 12 in the, block H, the normal direction of trafficbeing indicated by the I arrow. Inductive receiving coils 13, which may or maynot be provided withlla'minated iron cores, are located on the vehicle in front 'ofvthe leadingaxle thereof and in inductive relation to the track-rails 1. These receiving coils 13 are so connected that voltages induced therein byalternating currents flowing in opposite directions in the two track rails are cumulative. The receiving coils 13 are connected, through a circuit which is preferably tuned to resonance at the frequency of the train control current by the condenser 14, to a suitable amplifier A, preferably of the audion tube type. V p I The output circuit of the amplifier A is ing relay A070 and a valve relay VB, all of these relays being of a direct current type.

The secondary relay S is made slow acting by some suitable means such as the provision of a "copper. sleeve around its core to sustain the flux therein, the purpose of this slow-acting feature being hereinafter described. The acknowledging relay A070 is provided with two separate windings, one winding being connected in a pick-up circuit and the other in a stick. circuit as hereinafter described.

Two manually operable circuit controlling devices are provided in connection with the car-carried apparatus, these controlling devices being designated as the acknowledging contactor AC. and the reset contactor EC. The acknowledging contactor AC is provided with two contact fingers 16 and 17, the contact finger 16 being normally opened and the finger 17 being normally closed. The contactfinger 17 is so arranged that it does not disengage its front contact 18 until a given period of time after the finger 16 has engaged its back contact. Any suitable means may be provided for accomplishing this result, and in the drawings a simple flexible contact finger and dashpot arrangement has been shown. The acknowledging contactor AC is located in some convenient point, preferably in the locomotive cab within easy access of the engineer. The reset contactor RC is provided with a contact finger 19 which normally engages its front contact 20, and a contact finger 21 which is normally disengaged from its stationary back contact 22. This reset contactor RC is located at some point on the locomotive where it may be operated only from the ground, so that the locomotive must be brought to a stop before its operation can be efi'ected.

' Cab signals of any suitable type may or may not be provided in connection with the present invention. For the purpose of illustration, the cab signals G and B have been shown, it being understood that these signals comprise suitable lamps or other visible indicating devices located in the vehicle cab within view of the engineer.

The vehicle brakes may be automatically controlled in any one of a number of well known ways and by means of any suitable arrangementof devices. As the initiation of an automatic brake application is usually effected by some type of electro-pneumatic valve, the electro-pneumatic valve EPV has been illustrated, it being assumed that the deenergization of the windings of this valve initiates a restrictive automatic brake application, eventually bringing the vehicle to a stop. 1

Operation I The various circuits and devices have been shown in their normal condition, that is, with all circuits properly energized and the vehicle proceeding under clear traffic conditions. In order to simplify the wiring diagram, the letters B and C have been used to denote the positive and negative terminals of a suitable source of electrical energy, such as a storage battery or a turbo-generator.

VYith a vehicle traveling in a clear block, voltages of train control frequency are induced in the receiving coils 13, amplified by the amplifier A and act to energize the main car relay MR. With the main car relay energized, the secondary relay S is energized through the contact finger 23 of the main relay MR and a circuit which is obvious from the drawings. The valve relay VB is energized through the contact finger 24 andfront contact of the main relay MR, wires 25 and 26, as clearly shown. With the valve relay VB energized and the reset and acknowledging contactors in their normal positions, an energizing circuit for the electro-pneumatic valve EPV is completed which circuit may be traced as follows :from the battery terminal 13, contact finger 1-9 and front contact. 20 of the reset contactor RC, wire 27, contact finger 17 and front contact 18 of the acknowledging contactor AC, wire 28, contact finger 2-9 and front contact of the valve relay VR, wire 30 and the winding of the electro pneumatic valve EVP to the battery terminal C. With the electro-pneumatic valve EPV energized, the train under consideration may proceed in the clear block without automatic restriction, the engineer being informed of the fact that traffic conditions are clearby the indication of the clear cab signal G which is energized through the contact finger 31 and front contact of the main relay MR and a circuit which is'obvious'from the drawings.

Assume now that the train approachesthe entrance end of a block in which unfavorable traffic conditions exist, this block being the first block in the rear of an occupied or danger block and being hereinafter, designated as a caution block. If the engineer is alert and properlyv observes and recognizes the indication of the wayside signal at the entrance to the caution block, he'operates the acknowledging contactor AC just before the locomotive enters the caution block and re leases this acknowledging contactor shortly afterthis block is entered. When'the acknowledging contactor AC isdepressed with the vehicle still located in the clear block and the main'relay MR energized, a'pick-up cir cuit for the acknowledging relayAck is completechwhich circuit may betraced as follows :from the battery terminal B, Contact finger 16 and stationary contact 32 of the acknowledging contactorAC, wire :33, contact finger 34 and front contact ,of the valve relay VR, wires 35 and 36 and the winding 37 of the acknowledging rel-ayAcZe to the battery terminal C. It should be observed that acknowledging relay A070 :is properly picked up as described above, it is stuck up as soon as the loop 10 in question'is passed and the main relay is de-energized, through a stick circuit which may be traced as follows:fr,om the battery terminal B, contact finger 31 "and back contact of the main relay MR, wires 38, 39 and 40, contactfinger 41and front contact of the acknowledging relay A074 and wire 42 and the winding 43 .of the acknowledging relay A070 to the battery terminal C. It is .of -1 course understood that the engineer: must maintain the acknowledging contactor AC depressed until after .de-.energ'ization ofrelay MB to permit the stick Ci-IO11lt:jl15ll traced vto be completed,'it beingrememberedthat the Y slow acting characteristic of re'layiS maintains relay VR up until .afiterrelayM Rhas assumed its xdeene rgized :position. The energization of the acknowledging relay A0]? causes the valve relay .to :be energized through acircuit which maybe traced as follows ;from the battery terminal B, contact finger 44 and front contact ,of the, acknowl: edging relay A'cic, Wires 45 and 46 and the winding of the valve. relayVR to the battery terminal C. With the valve relay VRthus energized, the electroepneumatic valve E-PV is energized through'iits (circuit which has been traced above, 'and'the train under consideration may proceed through :thel'caution i block Without automatic restriction.

If the engineer is notgvigiflant and fails to acknowledge the caution signal before the relay S .hasdropped away, the pickup circuit for the acknowledging relay cannotwbe comvalve EPV, which circuit has been traced '1,

above,,and an automatic brake application re.- sults, bringing the train to a stop. lheengineer must then dismount from thecab and operate the reset contactor .RC, BthllS closing a pick-up circuit for the acknowledging relay 1.

Ack, which circuitmay be traced as follows from the battery terminal B, contact finger 31 and back contact of the main relay MR, wires 38, 39 and 47, contact fingerfZland stationary contact 22 of the reset contactor RC, wires 48 and 36and winding 37 of the acknowledging relay A010 to the battery terminal G. Once energized, the acknowledging relay A070 is maintained energized through the stick circuit traced above, the valve relay VB is energized through the contact fin ger 44 and the circuit traced, the energizing circuit for the electro-pneumatic valve EPV is closed at the contact finger 29 of the valve relay VB andthe engineer may then release the vehicle brakes and proceed in the caution block. It should be observed that the engineer can not defeat the operation of the automatic control by securing either the reset contactor BC or the'acknowledging contactor AG in their operated positions for the reason that both of these contactors are provided with normally closed contacts which are included in the energizing circuit for the electro-pneumatic valve EPV, and if either of these contactors were maintained in the operated position, this energizing circuit would be broken and anautomatic brake application would result.

Assume now that the train under consideras tion approaches the exit end of a caution block with the acknowledging relay properly energized by a previous acknowledgement or a reset as described above, and that the .wayside signal at the entrance end to the next block is in its stop or danger position, inclicating that the nextblock is occupied. As the trainreaches the end of thecaution block it encounters the acknowledging loop 10,

main relay MB is energized in response to the current flowing in the acknowledging loop 10 and breaks the stick circuit for A010 at contact finger 31. Depression of AC completes the pick-up circuit for the acknowledging relay A070 through the contact finger l6 and stationary contact 32 of the acknowledging contactor AC, this circuit having been traced above. As the train passes into the danger or occupied block beyond the loop 10, the main relay MB is again de-energized, retracting its contact finger 31 and thus again completing the stick circuit for the acknowledging relay A070, which circuit has been traced above. The train may now proceed in the danger block without automatic restriction, the vigilance of the engineer having been manifested by his proper acknowledg ment of the danger signal. :If'successive stop signals are encountered by the train under consideration, the acknowledging act ust described must be repeated by the engineer at.

vehicle has passed the loop 10, thus causing 1 de-energization of relay MR and relay S, this de-energization together with the de-energization of the acknowledging relay, causes the valve relay VR to be de-energized, thus breaking the energizing circuit to the electropneumatic valve EPV at the contact finger 29 of the valve relay VR', and initiating an automatic brake applicationas described above.

In applying a system of continuous train control to the track rails of existing railway systems, many points are encountered at which it is impossible to maintain the con tinuous flow of train control current in the track rails. This condition which occurs at switch frogs, cross overs and like points, would ordinarily cause the 'de-energization of the main relay MR and a consequent automatic brake application. In the system of the present invention, an automatic brake applicationas a result of these dead sections, as theyare ordinarily called, is prevented by the operation of the secondary relay S. This relay is made'slow-acting as set'forth above, and when the main relay MB is de-energized, retracting its contact finger 23 and thus deenergizing the secondary relay S, this relay S does not retract its contact finger 50 for a given interval of time, in general only a few seconds, after its de-energization. -The fact that the contact finger 5O of the secondary relay S remains in engagement with its front contact for a time interval after the main relay MB is de-energized insures that the valve relay VR be maintained energized while the dead section is being traversed,

the contact finger 50 and front contact of the secondary relay S maintaining an alternative energizing circuit for the valve relay VR through the wires 51, 26 and 46 as clearly shown in the drawings. The time required forthe secondary relay S to retract its contact finger 50 after the de-energization of the windings thereof is so arranged that the longest dead section ordinarily encountered in practice is traversed before this contact finger 50 is retracted, provided the train is proceeding at or above a given speed.

As described, the provision of the'slow acting relay S, avoids automatic brake applications due to so-called dead sections of track. With this relay S constructed to be slow acting, there might be thought to be a disadvantage, upon going from a caution into a danger block, since with no acknowl edgment, the train could proceed beyond the end of a loop 10 a distance depending upon the speed of the train and the time constant of the relay S, before suffering an automatic brake application. However this feature, as a defect, is more apparent than real, since the time constant of slow acting relay S is so small, at most only a few seconds, that the brakes are applied a very short distance beyond the end of a loop- 10, under the conditions just stated. 1

Furthermore the braking distance for an average train at average speed, is so great, that, to add to this braking distance a short distance due to the slow acting feature of re lay S does not materiallyincrease the distance that a train can proceed into a danger block under the conditions stated, before being brought to a stop. 1 v 7 Also, of course, the slow action of relay S adds a few seconds to the time during which the acknowledgment can be completed, but

this can in no manner be considered a disadvantage.

It is to be realized however that under such systems as the present, after anengineman has acknowledged onentering a caution block his vigilance can be depended upon to some extent upon entering a subsequent danger block or caution block as the case may be, to avert accident due to the capability of the train to enter into the danger or caution block in question acertain distance before being brought to a stop.

From the description above given itis seen that a system of automatic train control has been provided in which acknowledgment of all unfavorable signals is enforced, and in which successive danger or caution signals must be acknowledged to prevent an automatic brake application.

As the above inventionhas been described in connection with arather specific system of train control, it is to be clearly understood that certain changes, additons and modifications might be made without departing from the spirit of the invention as defined by the appended claims.

lVhat it is desired to secure by Letters Patent is 1. In an automatic train control system of the type in' which control influences corresponding to traffic conditions are continuously transmitted from the trackway to a moving. vehicle, car-carried control apparatus comprising a normally energized device for initiating a brake'application when de-energized, a stick relay having a pick-up circuit which may be manually closed only under favorable traffic conditions and for a short timeafter thecessation of. influence vorable traffic conditions for a limited distance of vehicle travel, whereby said pick-up circuit must be manually closed at said spaced points under unfavorable trafiic conditions to maintain said stick relay energized and to prevent the deenergization of said brake applying device.

2.111 an automatic train control system,

trackway apparatus for continuously transmitting electrical influences tovehicle receiv- 'ing means'under favorable traffi'c conditions and for cutting off said influences under unfavorable trafiic conditions, car carried apparatus comprising a normally energized brake applying device adapted to apply the vehicle brakes when de-energized, means for maintaining said brake applying device energized when said influences are being transmitted and for de-energizingsaid device a short time after said influences are cut off, a stick relay acting when energized to maintain said brake applying device energized while said influences are cut off, a'pick-up circuit forsaid stick relay including a manually operable circuit closer and a contact closed only under favorable traflic conditions ,and'for "a short time after the cessation of said influences, a stick circuit for said stickrelay closed only when said influences are cut 05, and means at spaced points along the trackway for transtrackway apparatus for transmitting influences to a moving vehicle continuously under favorable traflic condltions and for cuttlng off said influences under unfavorable trafiic conditions, vehicle carried apparatus comprising a main relay energized during the transmission of said influences, a brake applying device initiated to cause an automatic brake application a short time after said main relay is de-energized, means for maintaining said brake applying device inactive comprising astick relay, a pick-up circuit for said stick relay including a manually operable'circuit controller and a contact closed only when said main relay is energized and for a short time after de-energization'of said main re ay, a st ck circuit for said stick. relay til closed only when said main relay is de-energized, means forinitiating said brake applying device if said manually operable circuit controller is maintained closed for more than a predetermined time interval, and trackway means at spacedpoints for transmitting said influences for a limited distance of vehicle travel under all traffic conditions, whereby said manually operable circuit controller must be operated at each of said spaced points under unfavorable traffic conditions to prevent the initiation of said brake applying device. I .7

4. In an automatic train control system, in combination with track rails divided into blocks, trackway means for transmitting electrical influences continuously to receiving apparatus on a moving vehicle in each block under favorable trafiic conditions and for cutting off said influences under unfavorable traiiic conditions ahead,vehicle carried apparatus comprising a main relay, ener gi zed in accordance with the transmission of said influences," a valve relay energized in accordance withthe energization of said main relay and which willnot drop until a short time after de-energization of said main relay, a normally energized brake applying device acting when de-energized to initiate a brake application and being energized through a front contact of said valve relay, a stick relay acting when energized to maintain said valve relay energized, a pick-up circuit for said stickrelayincluding a manually operable circuit closerand a front contact of said valve relay, a stick circuit for said stick relay including a back contact of said main relay, and trackway means adjacent the exit end of each blockfor transmitting said influences for a limited distance of vehicle travel under all traflic conditions, whereby said' manually operable circuit closer must be operated upon each entrance of the vehicle into the next succeeding block When. unfavorable trallic conditions exist in that next block.-

5. In a train control system, a normally energized brake inltiatmg device made active by de-energization, a traffic responsive device for controlling energy flow to the brake device through the intermediaries of a slow acting relay and a valve relay, an energizing circuit for the slow acting relay running through a front contact of thetraflic responsive device, multiple branched energizing circuit for the valve relay with the branches running, respectively, through front contacts of the trafiic responsive device andthe slow acting relay, a stick. relay having a front for controlling energy' flow to the brake de vice through the intermediaries of a slow acting relay and a valve relay, an energizing circuit for the slow acting relay running through a front contact of the traffic responsive device, a multiple branchedenergizing circuit for the valve relay with the branches running, respectively, through front contacts of the trafiic responsive device and the slow acting relay, the energizing circuit for the circuit for the slow acting relay running through a front contact of the traffic responsive device, and a multiple branchedenergizing circuit for the .valve relay with the branches running, respectively, through front contacts of the traffic responsive device and the slow acting relay, the energizing cir cuitfor the brake device running through a front contact of the valve relay, and a stick device, capable of being picked up only when the valve relay is energized and of being stuck up only when the traffic responsive device is de-energized, for energizing the valve relay through an auxiliary circuit.

' 8. In an automatic train control system of the continuous .inductive typewherein continuously active acknowledging loops are employed near the exit end of each block for enforcing acknowledgments by the engineer of his, entrance into a danger block, the combination with a track divided into blocks each including the usual normally closed track circuit, means for causing the flow of alternating current insuch track circuit when the block next in advance thereof is unoccupied, a vehicle movable over said trackway, a main relay on said vehicle controlled in accordance with current in the track rails ahead of said vehicle, a slow acting relay controlled by said main relay, a'valve relay controlled by said slow acting relay, an electro-pneumatic brake control meanscontrolled by said valve relay, a stick relay which if energized maintains said'valve relay energized, said stick relay having a pickup circuit which may be closed only by the engineer if said valve relay is in its energized condition, and astick circuit for said stick relay c'losed'only ifsaid main relay 1 is in its de-energized condition.

9; In an automatic train control system of the continuous inductive type wherein con tinuously active acknowledging loops are emp'loyed near the exit end of each block for enforcing acknowledgments by the engineer of his entrance into a danger block, the combination With means partly on the vehicle and partly along the trackway for transmitting influences from the trackway to the vehicle throughout each block under clear tratlic con-- ditions and at the exit end of each block under caution and danger traflic conditions, a main relay on said vehicle energized in response to a such control influences, a slow acting relay controlled by said main relay, brake control means controlled by said slow acting relay, a stick relay, an auxiliary circuit for energizing said brake control means closed it said stick relay is energized, a pickup circuit for said stick relay including a contact only closed when said brake control means is in its normal condition, and a stick circuit for said stick relay including a contact closed only when said main relay is de-energized.

10. In an automatic train control system of the continuous inductive type wherein continuously active acknowledging loops are employed near the exit end of each block for enforcing acknowledgments by the engineer of his entrance into adanger block, the combination with means partly on the vehicle and partly along the trackway for transmitting influences from the trackway to the vehicle throughout each block under clear traflic conditions and at the exit end of each block under caution and danger traffic conditions, a main relay on said vehicle energized in response to such control influences, a slow acting relay controlled by said main relay, brake control means controlled by said slow acting relay, a stick relay, an auxiliary circuit for energizing said brake control means closed it said stick relay is energized, a pickup circuit for stick relay including a contact only closed when said brake control means is in its normal condition, and a supplemental pickup circuit for said stick relay including a contact closed only it said main relay assumes 1ts de-energized condition.

11. In an automatic train control system of the continuous inductive type wherein continuously active acknowledging loops are employed near the exit end of each block for enforcing acknowledgments by the engineer of his entrance into a danger block, the combination with means partly on the vehicle and partly along the trackway for transmitting influences from the trackway to the vehicle throughout each block under clear tratfic conditions and at the exit end of each block under caution and danger'traflic conditions, a main relay on said vehicle energized in response to such control influences, a slow acting relay controlled by said main relay, brake control means controlled by said slow acting relay, a stick relay, acknowledging means for closing a pickup circuit for said stick relay eflective only it said brake control means is in its normal inactive condition, reset means for pick- CHARLES S. BUSHNELL. 

